The first thing you notice is the video itself. The multi-camera LOOK AT ALL THESE PARTS I'M SINGING thing is pretty common for youtube singers and is pretty fertile for deconstruction on its own (why do you need us to see you're using a studio mic? if you were playing a piano, we'd just have a shot of your hands; why do you need to mug for the camera like you're on American Idol? oh wait; I just answered my own question), but this one's particularly noteworthy.

First, his head-bobbing and constant twitching away from the studio mic 4 inches from his face (and the cat), which would be UNBELIEVABLY HOT (the mic) if we were not in Baudrillard Hyperreality here, means he's either lipsynching or going through massive postproduction to change his levels. Either way, he is indeed fixing the tracks like crazy after the fact, which I'll get to later, but for now the question is: why bother? Why record yourself lipsynching shit nine times if it has nothing to do with the actual recording?

The reason is to trick the audience in to thinking his arrangements are more complex than they actually are. You can really see it in the Spark Mandrill piece; he splits melody/counterpoint lines like crazy so he can look like he's trading them across voice parts, and he even splits his simple/bad beatboxing. This would, again, be REALLY noticeable on the track unless he's either mixing it like crazy or actually only recording three or four parts + beatbox line. If you are not yet convinced he sucks, then at the very least he's pretty mendacious.

To be fair, he's doing video game songs, and moreover he's not doing anything past the PSX era when sound cards and memory actually started letting composers write interesting arrangements to go with their catchy, simple melodies, but to let him off the hook for this is to dare-I-say cheapen what you actually ought to be doing if you want a cappella to be interesting. Direct transcription is not only boring, but pointless, because you're never going to achieve the kind of fidelity you want with your voice. If you la la la your way through it you sound like a children's choir (which he does) and if you try to imitate instruments you're going to sound like an idiot. The key is to take an instrumental song and turn it into an interesting vocal piece*, which he's not even a little bit interested in doing.

And it makes sense that he's not, because oh god does this guy have zero confidence in his voice and technique. The first thing you need to "master" if you're going to be a good-to-great singer is breath technique. The reason for this is once you get some control over your general lung capacity and breathing, you can control your pitch to it and create I wide range of timbre, volume, range, etc. It really comes down to breath control. McGroove, however, spends 100% of his time in his head register, squeaking out the lightest falsetto possible. This is the hallmark of someone with no idea how to sing, because no singing requires less breath than a quiet falsetto. Of course, if you do that, you'll be working with an extremely limited range and even less volume, so it's a good thing none of his arrangements extend more than an octave or (and this is the really damning thing) require him to sing louder than piano.

Should I go on?

EDIT: Again, I'm not bothered by his success and I'm always happy to see somebody not have to work for a living. But video game songs, BECAUSE they're so catchy, iconic, and deeply simplistic, could produce some really interesting and fun vocal arrangement and one-man a cappella gives you the opportunity to play around with goofy arrangements without having to worry about what other singers can or want to do. It's a wasted opportunity.

*when people ask what I think a cappella covers should aspire to, I usually recommend the Real Group